bash script notes (1)
I tied to study the shell script a few times. But on that time, I didn’t get enough knowledge to deal with it. Now, I’m back.
Situation 1
I want to startup the vpn service when the computer startup. I added pon vpn_name to rc.local. However, this can be failed because when this line execute, the network may not be ready. So I decide to write a script to do this. It will wait until the Internet up. Here’s it.
#!/bin/bash
sleep_time=1
export PATH=$PATH:/usr/bin
while [ 1 ]
do
ping_success=`ping -c 1 -n vpn.yegong.net | \
sed -n -r 's/^.* (.) received.*$/\1/p'`
if [ $ping_success -eq 1 ]
then
pon yegong
exit 0
fi
sleep $sleep_time
sleep_time=$(expr $sleep_time + 1)
done
- export PATH is very important.
- `ping -c 1 -n vpn.yegong.net | sed -n -r ‘s/^.* (.) received.*$/\1/p’`, using ` surround the command to get the output text.
- sed -n -r ‘s/^.* (.) received.*$/\1/p’, using sed to simplify the output. It’s the regular expression. Very similar with VIM replace syntax, isn’t it?
- if [ $ping_success -eq 1 ], [ condition ] means the test program, equivalent to test condition, so man test will show more usage.
- sleep_time=$(expr $sleep_time + 1), it seems that every variable in shell is a string, so you can’t simply write x=x+1. Instead of, expr program read a string expression and output the results. Please notice the space in the expression.
Situation 2
For each text files in a directory, convert the file encoding to utf8.
There’s a simple util can guess the file encoding. It can be found at Wu Yongwei’s Programming Page (Can’t access when I write the article). Then I just need a script to combine the tellenc and iconv.
TMP_FILE="/tmp/utf8lize.output"
ENCODING="utf-8"
if [ $# == 0 ]
then
echo "Usage: utf8lize FILES"
exit 1
fi
for f in "$@"
do
if [ -f "$f" ]
then
enc=`tellenc "$f"`
if [ $enc != $ENCODING ] && [ $enc != "binary" ]
then
echo $f : $enc
cp "$f" "$f.bak"
iconv -f "$enc" -t "$ENCODING" -o "$TMP_FILE" "$f"
cp "$TMP_FILE" "$f"
rm -f "$TMP_FILE"
fi
fi
done
- $# results the number of arguments when it been executed.
- for f in “$@” is the for-each loop. And “$@” indicates the all program arguments. In addition, when you run the program utf8lize *, * will convert to filenames array. Using the ” to surrounding $@ can deal the filename with space.
on December 15th, 2009 | No Comments »
